A valve timing controller includes an outer rotor and an inner rotor rotating with a crankshaft and a camshaft, respectively, around a rotation axis. The inner rotor is relatively rotated inside the outer rotor to control valve timing according to the rotation phase between the outer rotor and the inner rotor by the relative rotation.
JP 4487957 B2 (corresponding to US 2007/0215085 A1) describes a valve timing controller equipped with a torsion coil spring wound in the shape of coil around a rotation axis. The torsion coil spring has a fixed end connected with the inner rotor, and a free end connected with the outer rotor. The torsion coil spring biases the inner rotor while being connected with the outer rotor by being twistingly deformed according to the relative rotation of the inner rotor to the outer rotor. Thereby, while an internal-combustion engine is stopped, the rotation phase can be forced to a phase suitable for starting due to the biasing force of the torsion coil spring. As a result, an expected valve timing will be realized.
The valve timing controller further includes a bush rotor projected coaxially from the inner rotor. The bush rotor supports the torsion coil spring in the radial direction to stabilize the biasing force of the torsion coil spring. The bush rotor has a cylindrical shape with a center axis aligned with the rotation axis. The torsion coil spring is a wound coil having a center axis aligned with the rotation axis. Since the orientation of the torsion coil spring supported by the bush rotor becomes difficult to change, it becomes possible to realize a predetermined valve timing by restricting the biasing force from being affected.